fixing RealtimeSleepTimer to work in concurrent threads

android/src/main/java/org/whispersystems/signalservice/api/util/RealtimeSleepTimer.java

@@ -10,9 +10,7 @@
 import android.os.SystemClock;
 import android.util.Log;
 
-import org.whispersystems.signalservice.api.util.SleepTimer;
-
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.ConcurrentSkipListSet;
 
 /**
  * A sleep timer that is based on elapsed realtime, so
@@ -21,41 +19,50 @@
  */
 public class RealtimeSleepTimer implements SleepTimer {
   private static final String TAG = RealtimeSleepTimer.class.getSimpleName();
+  private static ConcurrentSkipListSet<Integer> actionIdList = new ConcurrentSkipListSet<>();
 
-  private final AlarmReceiver alarmReceiver;
   private final Context context;
 
   public RealtimeSleepTimer(Context context) {
     this.context = context;
-    alarmReceiver = new RealtimeSleepTimer.AlarmReceiver();
   }
 
   @Override
   public void sleep(long millis) {
-    context.registerReceiver(alarmReceiver,
-                             new IntentFilter(AlarmReceiver.WAKE_UP_THREAD_ACTION));
+    final AlarmReceiver alarmReceiver = new RealtimeSleepTimer.AlarmReceiver();
+    int actionId = 0;
+    while (!actionIdList.add(actionId)){
+      actionId++;
+    }
+    try {
+      context.registerReceiver(alarmReceiver,
+             new IntentFilter(AlarmReceiver.WAKE_UP_THREAD_ACTION + "." + actionId));
 
-    final long startTime = System.currentTimeMillis();
-    alarmReceiver.setAlarm(millis);
+      final long startTime = System.currentTimeMillis();
+      alarmReceiver.setAlarm(millis, AlarmReceiver.WAKE_UP_THREAD_ACTION + "." + actionId);
 
-    while (System.currentTimeMillis() - startTime < millis) {
+      while (System.currentTimeMillis() - startTime < millis) {
         try {
           synchronized (this) {
             wait(millis - System.currentTimeMillis() + startTime);
           }
         } catch (InterruptedException e) {
           Log.w(TAG, e);
         }
+      }
+      context.unregisterReceiver(alarmReceiver);
+    } catch(Exception e) {
+      Log.w(TAG, "Exception during sleep ...",e);
+    }finally {
+      actionIdList.remove(actionId);
     }
-
-    context.unregisterReceiver(alarmReceiver);
   }
 
   private class AlarmReceiver extends BroadcastReceiver {
     private static final String WAKE_UP_THREAD_ACTION = "org.whispersystems.signalservice.api.util.RealtimeSleepTimer.AlarmReceiver.WAKE_UP_THREAD";
 
-    private void setAlarm(long millis) {
-      final Intent        intent        = new Intent(WAKE_UP_THREAD_ACTION);
+    private void setAlarm(long millis, String action) {
+      final Intent        intent        = new Intent(action);
       final PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
       final AlarmManager  alarmManager  = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);